The present invention relates to a fuel injection system for injection of fuel into an internal combustion engine, in particular for direct injection of fuel into the combustion chamber(s) of the internal combustion engine.
A fuel injection system is described in German Published Patent Application No. 197 25 076. It has a ring-shaped seal support for a sealing connection between a fuel injector and a respective connecting piece of a fuel distributor line, this seal support cooperating with a first sealing element for sealing the seal support with respect to an end face of an inlet section of the fuel injector and cooperating with a second sealing element for sealing the seal support with respect to the connecting piece of the fuel distributor line. A bushing insertable into a fuel inlet orifice of the inlet section passes through the ring-shaped seal support, so that the seal support is movably secured in the radial direction between an upstream collar of the bushing and the inlet section of the fuel injector.
One feature of the arrangement described in the aforementioned publication is that due to the total of two sealing elements, there are two components which may be subject to defects and may result in leakage in particular. The two sealing elements are installed one above the other and therefore may require vertical space. Since the sealing elements may not lie in direct contact with one another and sufficient material may be required to be available to fill out the ring grooves, the additional vertical space required for the seal support may not be insignificant. Another feature of the arrangement described in the aforementioned publication is that radial mobility of the seal support may be ensured only if it has a certain axial play and is not pressed by the bushing against the inlet section. Consequently, during installation the bushing may be required to be inserted into the fuel inlet orifice to a precisely defined depth and the bushing as well as the fuel inlet orifice in the fuel injector may be required to be manufactured to a very high precision.
A fuel injector which has an inlet section and is insertable into a receiving bore and is sealed by an O-ring on this inlet section with respect to a connecting piece of a fuel distributor line is described in Japanese Published Patent Application No. 08-312503. The O-ring is in sealing contact with an inside wall of the connecting piece.
One feature of this fuel injector may be that the deviations which may occur in the fuel injector relative to the fuel distributor line due to manufacturing tolerances may be compensated only by asymmetrical pinching of the O-ring inasmuch as the axes of the connecting piece of the fuel distributor line and the fuel injector are shifted relative to one another. This may result in leakage even with relatively minor pinching of the O-ring.
A fuel injection system according to the present invention may provide that deviations in the axial position of the connecting piece of the fuel distributor line and the fuel injector relative to one another may be compensated reliably. This may prevent unwanted warping of the fuel injector relative to the fuel distributor line. This may yield in particular a smaller vertical space required in comparison with the conventional seals, which may allow tolerances to be compensated. In an example embodiment, the inner sleeve and the outer sleeve may be connected by spiral springs.
Pressure equalizing bores may be provided in the outer sleeve to connect the fuel chamber to a clearance volume formed between the sealing edges of the sealing arrangement and the outer sleeve. The sealing arrangement may thus be acted upon by the pressure of the fuel over a larger extent of its cross section and the contact pressure of the sealing edges may be increased.
The seal support may be secured by a locking ring on the guide section of the fuel injector with its inner sleeve against the end face of the inlet section. A gap may remain between the end face of the inlet section and the outer sleeve of the seal support due to the elasticity of the sealing element even when acted upon by fuel under pressure. Even when the inner sleeve is pressed by the locking ring against the end face due to the manufacturing tolerances, the outer ring having the sealing element may retain its functionality.
In an example embodiment, the guide section is formed by a hollow screw which may be screwed into a threaded bore of the fuel injector and may hold the seal support against the fuel injector.
The outer ring may have an upstream peripheral conical chamfer arranged on the outside radially. This may facilitate insertion of the seal support into the connecting piece.